1. Field of the Invention
The present invention relates to irrigation systems and methods. More specifically, the present invention relates to an apparatus and method for avoiding backflow of water from an irrigation system to an associated water supply.
2. Description of Related Art
Irrigation not only permits foodstuffs to be grown, but also enables the cultivation of attractive plant life that otherwise would not have sufficient water to thrive. Many households now utilize sprinkler systems to provide irrigation in a comparatively uniform and trouble-free manner.
Often, a control unit such as a timer is used to regularly initiate operation of the sprinkler system to automatically provide the desired distribution of irrigation water. The timer is electrically connected to a plurality of electrically operated valves, each of which is able to permit water to flow into a corresponding zone of the sprinkler system. The valves must be individually activated so that the entire pressure and flow rate available will be focused on each zone, in turn.
In residential systems, the water for irrigation systems often is drawn from a supply of potable water. The irrigation system may be subject to a number of impurities such as fertilizers, pesticides, dirt, and insects, all of which may enter through sprinkler heads or other openings. Hence, it is desirable to avoid xe2x80x9cbackflow,xe2x80x9d or flow of irrigation water back into the water supply.
Unfortunately, although the water supply is usually positively pressurized with respect to the irrigation system, a reverse pressure gradient will sometimes exist due to the operation of valves and flow restrictors within the irrigation system. Hence, it is desirable, and in many locations, legally required, to use some type of backflow prevention device to avoid contamination of the water supply. Sometimes, backflow prevention devices known at atmospheric vacuum breakers (AVB""s) are sold in combination with valves; the valve and AVB combination is referred to as an xe2x80x9canti-siphoning valve.xe2x80x9d
AVB""s are tested according to the amount of backflow permitted by the AVB under normal irrigation system operating conditions. Backflow is measured in terms of the height of a column of water that is able to flow back through the AVB. The column is cylindrical with the same diameter as the conduit connected to the AVB. Thus, for example, the AVB may be required to allow passage of no more than a three-quarter inch diameter, three inch high column. Since backflow prevention requirements are typically established at a local level and vary from one locale to another, better performing AVB""s can be used in a larger number of localities.
Furthermore, it is desirable for an AVB to be simple to manufacture. Unfortunately, many known AVB""s have an inlet conduit that extends vertically, through an outlet conduit. Water entering the AVB from the side must therefore move laterally through a channel through the outlet conduit. This arrangement typically requires multiple manufacturing steps.
It is also desirable for an AVB to be as compact as possible. Compactness enhances the appearance and versatility of the AVB. Additionally, a compact AVB is lighter and less expensive to manufacture and ship than a less compact AVB. Furthermore, it is desirable for the AVB to have the smallest possible xe2x80x9chead loss,xe2x80x9d or pressure drop, so that the pressure of the irrigation water will be sufficient to enable the water distribution units to operate effectively.
Hence, it would be an advancement in the art to provide a backflow prevention apparatus and method that provides effectively by permitting only a relatively small amount of backflow under normal irrigation system operating conditions. It would be a further advancement in the art to provide a backflow prevention apparatus and method that is simple, inexpensive, easy to assemble, and reliable in operation. Yet further, it would be an advancement in the art to provide a backflow prevention apparatus and method that is comparatively compact and has a small associated pressure drop.
The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available backflow prevention systems and methods. Thus, it is an overall objective of the present invention to provide backflow prevention devices and associated methods that remedy the shortcomings of the prior art.
To achieve the foregoing objective, and in accordance with the invention as embodied and broadly described herein in the preferred embodiment, an irrigation system is used to irrigate an area. The irrigation system has a valving system designed to control flows of irrigation water to a plurality of water distribution units such as sprinklers. The sprinklers receive irrigation water from a plurality of distribution conduits, each of which is in communication with an anti-siphoning valve. Each anti-siphoning valve has a valve and an anti-siphoning device.
Each anti-siphoning valve also has a pair of wires that conveys a valve activation signal to the valve to move the valve between open and closed configurations. The anti-siphoning valves may be connected to a feeder conduit to form a manifold that receives water from a main line. The manifold is disposed underground, and the anti-siphoning valves may extend upward, above-ground from the feeder conduit. Control unit wires extend from the valve wires to a control unit such as a timer.
According to one exemplary embodiment, the anti-siphoning device has a housing, a plunger, a plunger retainer, and a cap. The housing has an inlet channel and an outlet channel. The outlet channel is defined by an interior wall, and the inlet channel is defined by the combination of the interior and exterior walls. The inlet channel has an inlet orifice with a generally annular shape, and the outlet channel has an outlet orifice with a generally circular shape. A plunger cavity is disposed adjacent to the inlet and outlet orifices.
The plunger is disposed in the plunger cavity. The plunger has an annular portion with a central opening generally aligned with the outlet orifice. The plunger also has a plurality of orientation posts that extend away from the orifices and toward the plunger retainer.
The plunger retainer has a lip that extends generally upward and a retention plate in which a plurality of slots and orientation holes are formed. The orientation posts pass through the orientation holes to keep the annular portion of the plunger oriented generally parallel to the orifices. The slots permit air to flow through the retention plate when the annular portion is disposed to unblock the slots.
The cap has a roof supported by a plurality of struts such that vents are defined between the struts. The vents permit ambient air to flow into the cap. The cap is attached to the lip of the plunger retainer.
The plunger cavity is sized such that the plunger is able to move between an open position and a closed position. In the open position, the plunger abuts the retention plate, but is displaced from the inlet orifice so that irrigation water is able to flow relatively freely from the inlet orifice to the outlet orifice through the plunger cavity. The slots of the retention plate are blocked by the annular portion of the plunger so that air is unable to enter the plunger cavity. In the closed position, the plunger abuts the inlet orifice so that irrigation water is unable to flow from the outlet orifice to the inlet orifice. Air is able to enter the plunger cavity via the slots, and is able to move through the plunger via the central opening of the annular portion to reach the outlet orifice.
Thus, the anti-siphoning device permits irrigation water to flow from the inlet channel into the outlet channel. However, flow in the opposite direction (e.g., backflow) is rapidly cut off. Instead, air is permitted to enter the outlet channel to dispel the vacuum effect that tends to cause backflow.
The various parts of the anti-siphoning device may be easily and inexpensively manufactured by a method such as injection molding. In certain embodiments, the housing may be injection molded such that the interior and exterior walls are unitarily and simultaneously formed with the remainder of the housing. The plunger may include a plastic core made by injection molding. The plastic core may be inserted into another mold, into which some type of molten elastomer is injected to form the elastomeric exterior around the plastic core. The cap and the plunger retainer may also be injection molded, and the cap may be permanently attached to the plunger retainer by a method such as welding. The cap/plunger retainer, the plunger, and the housing may then be assembled to form the anti-siphoning device.
Through the use of the apparatus and method of the invention, backflow from irrigation systems may be considerably reduced. The annular shape of the plunger provides rapid and effective sealing to enhance the backflow prevention performance of the anti-siphoning device. Furthermore, the anti-siphoning device may be easily and inexpensively manufactured with a small number of manufacturing steps. Yet further, the anti-siphoning device is comparatively compact and has a small associated pressure drop.